Thank you for reaching out!
The tiers are no longer based on the OWGR (Official World Golf Ranking), since the Majors this year will include LIV golfers whose World Ranking will no longer be indicative of their probable performance.
So starting this year, we are using the "to win" betting odds of each golfer to determine the tiers they are included in. Our odds are based on an average of all the sportbooks in SportRadar. Once posted, our tiers will not change.
Please let me know if you have any other questions or concerns. Have a great day!